1. Field of the Invention
This invention relates to incinerators for oil-containing sludges and incineration methods therefor.
It is well-known to use activated white clay in the purification of edible oils, petroleum and the like but the conventional methods heretofor proposed for the treatment of the wasted sludges containing oil have not yet been quite satisfactory.
Wasted white clay after the use generally takes the form of slurry containing oils, swells by the absorption of water if left as it is and does not solidify like ordinary mud even if exposed to the sun light. Therefore, it can not be utilized for land reclamation or left as it is. Moreover, such type of sludge may even cause spontaneous combustion if it is left for a long time while exposed to the sun.
In order to overcome these problems, it has been proposed to burn and remove the oil contents in the waste sludge. In the combustion of waste white clay containing oils, the crystal structure of the activated white clay is destroyed by the heating to approximately above 600.degree.C and, thereafter, the white clay loses its water absorption property and, hence, aforesaid tendency of swelling due to the water absorption. The waste white clay leaves, after the burning, ash components containing silica, alumina, trace amount of iron oxides, etc. which can be utilized as the aggregate material for fire-proof buildings.
2. Description of the Prior Art
Conventional incinerators, for example, multi-tray type, rotary kiln type, stepped bed type and the like can generally be employed for continuous combustion but, since the waste white clay is composed of fine powder and contains oil contents therein, it takes much time to heat the clay to a desired temperature, and therefore the incineration is time consuming and inefficient. In addition, continuous incineration operation at higher temperatures above 600.degree.C is rather difficult because of the structure of the furnaces, which results in unburned portions in the incineration ash to produce a somewhat black powder. Although several other methods have been proposed such as a method of incinerating the waste white clay by spraying, or a method of using a fluidized bed incinerator in which the waste clay is fluidized together with sand, or a method by way of liquefying and atomizing the clay, all of these methods are defective in that complete combustion is difficult and finely powdered ashes are produced resulting in fine dust in the exhaust gas, and are thus inconvenient to be disposed with. In addition, they have an disadvantage that the waste white clay is melted at temperatures above 900.degree.C in the incineration operation and deposited onto the surface of the furnace wall to damage the furnace thereby hindering the continuous incineration.